In recent years the involvement of the hepatic mixed function oxidase system in carcinogenesis has become increasingly evident. The role of similar systems in extrahepatic tissues remains to be explored. During the past year, we studied the mixed function oxidase of mammary gland microsomes from lactating rats and developed a procedure for detection of cytochrome P-450 and its 3-methylcholanthrene- and Beta-naphthoflavone-inducible form, cytochrome P-448. Pretreatment of lactating rats with these inducers also increased the capacities of mammary gland microsomes for hydroxylation of benzo (alpha) pyrene and N-2-fluorenyl-acetamide (2-FAA). Yields of the hydroxy products of 2-FAA per unit of cytochrome P-448 were higher in mammary gland than in liver microsomes suggesting that mammary gland cytochrome P-448 is a more efficient catalyst of the hydroxylation than the hepatic species. We propose to examine the binding affinities of these 2 species for 2-FAA, a type I substrate. We also propose to determine the extent of conversion by mammary gland microsomes of 2-FAA to N-hydroxy-2-FAA, a required intermediate for carcinogenesis. The activity of cytochrome c oxidase in mammary gland mitochondria was similar to that of liver mitochondria. Because certain metabolites of 2-FAA, o-aminophenols, are oxidized by the mitochondrial enzyme to o-quinoneimines which are capable of interacting in vitro with proteins, we shall investigate this oxidative metabolic pathway in the mammary gland. We observed that activities of carcinogen-metabolizing enzymes are altered in livers of nursing rat pups when the mother is treated with inducers of hepatic enzyme(s). Factor(s) altering these enzyme activities are apparently transmitted by milk. To elucidate the mechanism of transmission of a drug (carcinogen) from a mother to her young, we shall focus our research on 2 areas: 1) assessment of the carcinogenicity of milk of carcinogen-treated lactating rats for their young, and 2) determination of metabolites of the carcinogen in milk. For determination of microsomal and mitochondrial metabolites of 2-FAA as well as those in milk we propose to use high pressure liquid chromatography.